DE19601281A1 - High yield and high purity bis-2-chloro-ethoxy-methane preparation - Google Patents

Abstract

Preparation of bis(2-chloroethoxy)methane of high purity involves reacting 2-chloroethanol and paraformaldehyde with a stoichiometric excess of 2-chloroethanol of at least 2.05 at 50-120 deg C in the presence of an acid mixed catalyst. The catalyst comprises: (a) hydrogen chloride as volatile acid; and (b) p-toluenesulphonic acid or a cation exchanger as involatile acid in concentrations of 0.005-0.5 mole hydrogen chloride, 0.0005-0.2 mole p-toluenesulphonic acid or 0.002-0.2 mole acid equivalent of the cation exchanger per mole formaldehyde. The two catalyst components are separated after reaction.

Description

The invention relates to the production of bis (2-chloroethoxy) methane from 2-chloroethanol and Paraformaldehyde in the stoichiometric excess of 2-chloroethanol in the presence of acid Catalysts. The bis (2-chloroethoxy) methane is mainly used for the synthesis of liquid Polysulfide polymers used. The purity of the product becomes essential from the purity of the 2-chloroethanol used and determined by the synthesis conditions.

The synthesis of bis (2-chloroethoxy) methane has been widely described in the literature. she can be influenced by suitable catalysts. In addition to hydrochloric acid (Adams, Adkins: JACS 47, 1358 (1925)) the use of ammonium chloride and calcium chloride (Org. Synth. 1, 1 (1932)), ferric chloride (Adams, Adkins: JACS 47, 1358 (1925) and 49, 2517 (1927)), Pyridine hydrochloride and sodium bisulfate (Adams, Adkins: JACS 49, 2517 (1927)) as well as calcium chloride / hydrogen chloride (Freudenberg, Acker: Ber. 74, 1404 (1941)) described.

Patents describe hydrogen chloride (DD 2 51 257), organic sulfonic acids (POL 51 701), Hydrogen bromide / hydrogen chloride (DD 1 12 118) claimed as catalysts.

The conversion of hydrogenated with hydrogen chloride or calcium chloride / hydrogen chloride Paraformaldehyde with 2-chloroethanol has the disadvantage that in addition to the bis (2- chlorethoxy) methane form up to 15% of the undesirable bis (2-chloroethoxymethyl) ether. The content of this ether depends on the temperature, the ratio of 2-chloroethanol / Formaldehyde and the quality of the paraformaldehyde used. With a molar Ratio of 2-chloroethanol to formaldehyde of about 4.5 are considered with hydrogen chloride Catalyst depending on the synthesis conditions contents of bis (2- chloroethoxymethyl) ether between 0.8 and 1.3% reached (DE 42 14 847).

The bis (2-chloroethoxymethyl) ether forms polysulfide compounds analogously to the bis (2-chloroethoxy) methane, which, however, easily release formaldehyde. This free formaldehyde can be too Formic acid are oxidized, which in turn hydrolytically cleaves the Polysulfide molecule takes place. For this reason, a product for polysulfide production  required that less than 1.5%, better less than 0.8% of the bis (2-chloroethoxymethyl) ether contains.

The use of mixtures of hydrogen chloride / hydrogen bromide (DD 1 12 118) is said to lead to a reduction in the bis (2-chloroethoxymethyl) ether content below 1%. The disadvantage is however, that the product mixture is contaminated with bromine substitution products. In addition, the catalyst cannot be recovered.

The reaction of paraformaldehyde with 2- Chloroethanol lowers the undesirable ether content to 0.5% (POL 51 701). It forms But bis (2-chloroethyl) ether, because the organic sulfonic acids in their Acid strength of the strong mineral acids come close. The yields in this reaction are lower than with the reactions of paraformaldehyde catalyzed with hydrogen chloride 2-chloroethanol.

Other catalysts, such as the Lewis acids iron (III) chloride and zinc (II) chloride, remain in the sump after the reaction and thus lead to discoloration of the bis (2- chloroethoxy) methane. These substances can only be separated with considerable effort will. The use of such catalysts also leads to poorly soluble dark Deposits on the walls of the reaction vessel.

The object is to catalyze the preparation of bis (2-chloroethoxy) methane in such a way that minimizes the formation of unwanted by-products, high conversion of paraformaldehyde reached and the bottom product bis (2-chloroethoxy) methane without further work-up steps in the synthesis of polysulfide polymers can be used.

According to the invention the object is achieved in that 2-chloroethanol in the stoichiometric Excess of at least 2.05 at temperatures of 50 to 120 ° C in the presence of a acid mixed catalyst consisting of hydrogen chloride as volatile acid and p-toluene sulfonic acid or a cation exchange resin as a non-volatile acid in concentrations from 0.005 to 0.5 mol of hydrogen chloride, 0.0005 to 0.2 mol of p-toluenesulfonic acid or with a Acid equivalent of the cation exchange resin from 0.002 to 0.2 mol per mole of formaldehyde  Paraformaldehyde implemented and the two catalyst components on different, however, be separated in a manner known per se and returned to the reaction.

The catalyst components are preferably used in concentrations of 0.005 to 0.2 mol Hydrogen chloride, 0.001 to 0.1 mol of p-toluenesulfonic acid or with an acid equivalent of 0.005 to 0.1 mol of cation exchanger used per mole of formaldehyde.

It was found completely surprisingly that the content of the undesired by-product Bis (2-chloroethoxymethyl) ether significantly reduced by using these catalyst systems without side reactions, such as the formation of bis (2-chloroethyl) ether, run and without the need for complicated refurbishment operations. The volatile acid is usually used in excess. The Removal of the reaction mixture from the catalyst is completely unproblematic because the Hydrogen chloride is also exaggerated in the azeotropic distillation and the p-toluene sulfonic acid or the ion exchanger are removed from the reaction mixture by filtration separates.

It is advantageous that the considerable reduction in the bis (2-chloroethoxymethyl) ether Content of the molar excess of 2-chloroethanol up to close to the theoretical limit can be reduced. Another advantage is that the catalyst components are light can be separated and returned to the process.

example 1

60 g of paraformaldehyde, 604 ml of a 99.3% 2-chloroethanol (this corresponds to one Mol ratio 2-chloroethanol: aldehyde of approx. 4.5) and the catalyst mixture are in a 2 l three-necked flask with stirrer, dephlegmator and internal thermometer. After The reaction is carried out under the reaction conditions given in Table 1 the reaction product worked up by distillation. At a vacuum of 180 to 100 torr First the water of reaction / 2-chloroethanol azeotrope is removed (first run).

Then the excess 2-chloroethanol used together with the HCl in Va distilled off in a vacuum at 100 to 20 torr (flow 2). Preliminary run 1 is under extraction throw. Preliminary run 2 is used again as a return product in the reaction.  

The distillation bottoms also contain the desired bis (2-chloroethoxy) methane higher-boiling impurities, such as those in the further processing to polysulfide polymers disruptive bis (2-chloroethoxymethyl) ether. The p-toluenesulfonic acid (p-TSS) is through simple filtration separated from the reaction mixture and the starting catalyst mixture added again. The reaction mixtures then contain a maximum of 0.04% by weight of acid.

Table 1

Yields of bis (2-chloroethoxy) methane 1 and contents of bis (2-chloroethoxymethyl) ether 2 depending on the catalyst system and synthesis conditions (starting molar ratio 2-chloroethanol: formaldehyde approx. 4.5)

From Table 1 it can be seen that when using catalyst mixtures according to the invention Yields of 1 of more than 95% and contents of 2 below 0.8% can be achieved. in the In comparison, the sole use of hydrogen chloride as a catalyst Keep 2 above 0.8%. When using p-toluenesulfonic acid alone only yields well below 90% achieved.  

Example 2

604 ml of a 99.3% 2-chloroethanol and the catalyst mixture are in a 2 l Three-neck flask with internal thermometer and dephlegmator. The mixture is heated to 110 ° C and after reaching this temperature adds 60 g of paraformaldehyde. The molar ratio of 2-chloroethanol to formaldehyde is approximately 4.5. The reaction mixture becomes half Leave at this temperature for one hour.

The water of reaction / 2-chloroethanol azeotrope is then added by distillation in vacuo 180 to 100 torr or removed under normal pressure (lead 1). After that it will be in excess 2-chloroethanol used together with the HCl in vacuo at 100 to 20 torr distilled off (flow 2).

Preliminary run 1 is subjected to the extraction. Preliminary run 2 will be returned to the Reaction used. The p-toluenesulfonic acid (p-TSS) is removed by simple filtration Separated reaction product and added to the starting catalyst mixture again.

Table 2

Yields of bis (2-chloroethoxy) methane 1 and contents of bis (2-chloroethoxymethyl) ether 2 depending on the catalyst system and workup (starting molar ratio 2-chloroethanol: formaldehyde approx. 4.5)

It can be seen from Table 2 that when using catalyst mixtures according to the invention yields of bis (2-chloroethoxy) methane of more than 90% and contents of bis (2-chloroethoxymethyl) ether below 0.8% can be achieved. in the In comparison, the sole use of hydrogen chloride as a catalyst Contents of bis (2-chloroethoxymethyl) ether above 0.8%. When using only p-toluenesulfonic acid yields are only below 85%.

Example 3

A corresponding to the specified molar ratio of 2-chloroethanol to formaldehyde Amount of a 99.1% 2-chloroethanol is mixed with a catalyst mixture of 2 ml HCl and 3.44 g of p-toluenesulfonic acid in a 2 l three-necked flask with an internal thermometer and Dephlegmator presented and heated to 110 ° C. After reaching this temperature 60 g of paraformaldehyde were added. The catalyst concentrations correspond to one Ratio of 0.01 mol / mol formaldehyde. The reaction mixture is at half an hour leave this temperature.

Then the water of reaction / 2-chloroethanol azeotrope under normal pressure removed by distillation (flow 1). Then the excess 2-chloroethanol distilled together with the HCl in vacuo at 100 to 20 torr (lead 2).

Preliminary run 1 is subjected to the extraction. Preliminary run 2 will be returned to the Reaction used. The p-toluenesulfonic acid (p-TSS) is removed by simple filtration Separated reaction product and added to the starting catalyst mixture again.

From Table 3 it can be seen that when the molar ratios of 2-chloroethanol vary Formaldehyde under otherwise identical synthesis conditions with decreasing molar ratios Decrease yields on 1 and increase the contents on 2. The fact is remarkable that below the molar ratio of 2.7 when using only HCl the content of 2 is clearly above 1.5%, while it is when using the invention Catalyst combination below 0.8%.  

Table 3

Yields of bis (2-chloroethoxy) methane 1 and contents of bis (2-chloroethoxymethyl) ether 2 depending on the molar excess of 2-chloroethanol compared to the formaldehyde (catalyst concentrations HCl and p-TSS each 0.01 mol / mol formaldehyde)

Example 4

403 ml of a 99.4% 2-chloroethanol are in a 2 l three-necked flask with a stirrer, Submitted internal thermometer and dephlegmator and with 2 ml of concentrated hydrochloric acid as well 10 g of freshly activated cation exchanger with an exchange capacity (acid equivalent) of 1.8 mmol / ml ion exchanger. This corresponds to a maximum acidity concentration of 0.01 mol / mol formaldehyde. The mixture is heated to 110 ° C. and then given When this temperature is reached, 60 g of paraformaldehyde are added with stirring. The molar ratio of 2- Chloroethanol to formaldehyde is approximately 3. The reaction mixture is at half an hour maintained at this temperature and stirred.

The water of reaction / 2-chloroethanol azeotrope is then added by distillation in vacuo 180 to 100 torr removed (lead 1). Then the 2- used in excess Chlorine ethanol was distilled off together with the HCl in vacuo at 100 to 20 torr (flow 2). Preliminary run 1 is subjected to the extraction. Preliminary run 2 will be returned to the Reaction used. The ion exchanger is separated from the reaction by simple filtration product separated and sent for reactivation.

The yield of bis (2-chloroethoxy) methane 1 is 90.5% and the content of bis (2- chloroethoxymethyl) ether 2 0.55%. In contrast, with a cation exchanger  Use of 2 g (corresponds to an acid equivalent of 0.0018 mol / mol formaldehyde) same reaction conditions and similar yield 1.18% of 2 obtained.

The advantage of using ion exchangers over p-toluenesulfonic acid is in that no contents of non-volatile acid remain in the reaction product.

Claims (4)

1. A process for the preparation of bis (2-chloroethoxy) methane of high purity from 2-chloroethanol and paraformaldehyde in the stoichiometric excess of 2-chloroethanol by means of acidic catalysts, characterized in that 2-chloroethanol in the stoichiometric excess of at least 2.05 at temperatures from 50 to 120 ° C in the presence of an acidic mixed catalyst consisting of hydrogen chloride as volatile acid and p-toluenesulfonic acid or a cation exchanger as non-volatile acid in concentrations of 0.005 to 0.5 mol hydrogen chloride, 0.0005 to 0.2 mol p- Toluene sulfonic acid or with an acid equivalent of the cation exchanger of 0.002 to 0.2 mol per mole of formaldehyde are reacted with paraformaldehyde and the two catalyst components are separated off. 2. The method according to claim 1, characterized in that the catalysts in conc trations of 0.005 to 0.2 mol of hydrogen chloride and 0.001 to 0.1 mol of p-toluenesulfonic acid each Mol formaldehyde can be used. 3. The method according to claim 1, characterized in that the catalysts in one Concentration of 0.005 to 0.2 mol of hydrogen chloride and with an acid equivalent of 0.005 to 0.1 mol of cation exchanger per mole of formaldehyde can be used. 4. The method according to claim 1 to 3, characterized in that both catalyst Components separated in different, but in a conventional manner and in the Reaction can be attributed.